=item B<new>
 
Create a new instance of an C<Astro::Flux> object.
 
  $flux = new Astro::Flux( $quantity, $type, $waveband );
 
The first three parameters must be defined. They are:
 
  quantity - numerical value for the flux, my be a primitive, or a
             C<Number::Uncertainty> object.
  type - type of flux. Can be any string.
  waveband - waveband for the given flux. Must be an C<Astro::WaveBand> object.
 
If any of the parameters are undefined, the constructor will throw
an error. If the waveband parameter is not an C<Astro::WaveBand> object,
the constructor will throw an error.
 
The type is case-insensitive for lookups using the C<quantity> method.
 
A fourth optional argument may be passed; this is a hash containing
the following optional keys:
 
  quality - an C<Misc::Quality> object denoting quality flags for the
    C<Astro::Flux> object.
  reference_waveband - an C<Astro::WaveBand> object denoting a reference
    waveband for the C<Astro::Flux> object. This is used for determining
    magnitudes when deriving them from C<Astro::FluxColor> objects. See
    C<Astro::Fluxes>.
  datetime - an C<DateTime> object which is the datetime of observation for the
    measurement in the C<Astro::Flux> object.
  obsid - An array reference to a list of observation identifiers. Can be
    used to identify the observation(s) from which this measurement was
    taken (e.g. from a filename).
 
=cut
 
sub new {
  my $proto = shift;
  my $class = ref( $proto ) || $proto;
 
  my $quantity = shift;
  my $type = shift;
  my $waveband = shift;
 
  my %args = @_;
 
  croak "Quantity must be defined"
    unless defined $quantity;
 
  unless ( UNIVERSAL::isa($quantity, "Number::Uncertainty" ) ) {
     $quantity = new Number::Uncertainty( Value => $quantity );
  }
 
  croak "Type must be defined"
    unless defined $type;
 
  croak "Waveband must be defined"
    unless defined $waveband;
 
  unless ( UNIVERSAL::isa($waveband, "Astro::WaveBand") ) {
     $waveband = new Astro::WaveBand( Filter => $waveband );
  }
 
  my $flux = {};
 
  $flux->{QUANTITY} = { uc($type) => $quantity };
  $flux->{WAVEBAND} = $waveband;
  $flux->{TYPE} = uc( $type );
 
  if( defined( $args{'quality'} ) &&
      UNIVERSAL::isa( $args{'quality'}, "Misc::Quality" ) ) {
    $flux->{QUALITY} = $args{'quality'};
  }
  if( defined( $args{'reference_waveband'} ) &&
      UNIVERSAL::isa( $args{'reference_waveband'}, "Astro::WaveBand" ) ) {
    $flux->{REFERENCE_WAVEBAND} = $args{'reference_waveband'};
  }
 
  if( defined( $args{'datetime'} ) &&
      UNIVERSAL::isa( $args{'datetime'}, "DateTime" ) ) {
    $flux->{TIME} = $args{'datetime'};
  }
 
  if( defined( $args{'obsid'} ) ) {
    $flux->{OBSID} = $args{'obsid'};
  }
 
  bless( $flux, $class );
  return $flux;
 
}